The present invention relates to caul plates for the manufacture of rigid wood products by compression of coarse wood particles.
Textured caul plates having a wood-grain pattern have heretofore been photoengraved or etched in a costly manufacturing process. An example of photoengraving as applied to caul plates is described in U.S. Pat. No. 4,544,440. A blank caul plate element is suitably coated with a photosensitive etchant resist and a wood grain pattern is projected by ultraviolet light upon the resist so as to alter the solubility of portions thereof. The blank is immersed in acid and the wood grain pattern if formed at the surface of the blank. In a second example of an etching process, a blank caul plate receives a coating of etchant resist and a small roll engaging the blank carries a stainless steel matrix upon its outer periphery, the matrix having a hand carved wood-grain pattern upon its exposed surface. The roll contacts the blank and rotates to wear down the resist material and expose portions of the blank so as to transfer the wood-grain pattern. The blank is immersed in acid to erode portions of the blank no longer protected by the resist material and transfer the wood-grain pattern to the surface of the blank. Manufacturing costs associated with etching process can exceed eight thousand dollars per caul plate and the caul plate is susceptible to damage in use. In addition to the manufacturing expense and risk of damage, such caul plates usually carry but one pattern and require remounting when a different pattern is desired.